Booster vaccination of adults with reduced-antigen-content diphtheria, Tetanus and pertussis vaccine: Immunogenicity 5 years post-vaccination

At 60 months post-vaccination, adults (mean age 45.6 years) randomised to receive combined reduced-antigen-content diphtheria-tetanus and acellular pertussis vaccine (dTpa) versus tetanus-diphtheria (Td) + monovalent acellular pertussis (pa) were seroprotected against diphtheria (≥0.016 IU/mL Vero cell assay) and tetanus (≥0.1 IU/mL ELISA assay) in 94.4% and 96.2%, respectively (dTpa), compared with 93.7% and 90.6% (Td + pa). Anti-FHA, anti-PT and anti-PRN antibodies (≥5 EL.U/mL) were maintained in 100%, 89.5% and 95.0% of dTpa versus 100%, 85.5% and 90.6% of pa vaccine recipients. At 5 years post boosting, antibody levels to diphtheria and tetanus are similar amongst adults receiving a dTpa or dT, and pertussis antibodies remain above pre-booster levels in at least 85%.